Apparatus and method for field calibration of nuclear surface density gauges

Nuclear gauge density measurements are routinely used for compliance verification with specifications for road and construction projects. The density of construction materials is an important indicator of structural performance and quality. Due to speed of measurement, flexibility and accuracy, nuclear gauge density measurement methods are becoming the preferred standard around the world. Requirements dictate that gauges be verified or calibrated once every 12 to 18 months. Presently, there are no field portable devices available for verification of the gauge calibration. Also, the density references used for calibration of gauges, are large and not designed for field portability. Therefore, to meet the present standards, users are required to ship gauges back to a service facility for calibration. This paper presents results obtained by a newly developed device for field verification and calibration of nuclear density gauges from three different manufacturers. The calibrations obtained by this device are compared to the factory calibration methods and accuracies are reported for each gauge model